VendorInvestigate result on a Shenzhen dulaglutide lot lands 2.0 points below the supplier’s figure
A reminder that a purity figure is the output of a method, and that methods differ.
Callum Brathwaite
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Archive — page 3
134 piecesWhere the solvent front ends is a decision, not a fact
The denominator excludes solvent-front features and injection artefacts by convention. Conventions differ on where the front ends, and a fragment eluting early exists in one…
Bacteriostatic water, sterile water, and the 0.9 per cent that makes the difference
At low concentrations a measurable fraction of peptide can adsorb to glass and plastic surfaces, and the loss is largest exactly where it is least expected.
Sterility is not a percentage, which is the whole difficulty
Every certificate circulating in this market answers a question about molecules. Almost none answers a question about organisms, pyrogens, or the integrity of the seal.
Independent analysis puts a QST dulaglutide lot at 95.4%, against 91.5% on the certificate
The report states the gradient, the wavelength and the integration threshold, which is more than most.
PeptideMeter result on a Hong Kong mazdutide lot lands 2.6 points below the supplier’s figure
The result is unremarkable. What the report omits is not.
Accuracy, precision and the tolerance nobody states
Parts per million sound impressive until they are converted into daltons at the molecular weight of the thing being measured.
Storage after reconstitution, and the evidence behind the numbers
A needle blunts on first use. Reuse is uncomfortable, and it is a documented contributor to lipohypertrophy.
VendorInvestigate result on a Changsha liraglutide lot lands 3.2 points below the supplier’s figure
A reminder that a purity figure is the output of a method, and that methods differ.
Bacteriostatic water, sterile water, and the 0.9 per cent that makes the difference
We set out what is known, what is inferred and what is simply assumed about the fortnight after a vial is opened.
Resolving power and mass accuracy are two different specifications
Parts per million sound impressive until they are converted into daltons at the molecular weight of the thing being measured.
Same mass, different molecule: why identity by mass is not identity
Reversed-phase chromatography runs in an organic, acidic mobile phase that dissociates most non-covalent aggregates on the way to the detector.
Units, millilitres, milligrams: three scales on one small object
We work through the arithmetic in full, because it is short, and because the errors it prevents are order-of-magnitude errors.
Medutest result on a Xi'an orforglipron lot lands 1.0 points below the supplier’s figure
The report states the gradient, the wavelength and the integration threshold, which is more than most.
Independent analysis puts a JEEP retatrutide lot at 97.1%, against 94.3% on the certificate
A reminder that a purity figure is the output of a method, and that methods differ.
Endotoxin is not a microorganism, and killing the bacteria does not remove it
Three compendial method families are in routine use and a fourth, based on a recombinant enzyme rather than crab lysate, is now compendial in its own right.
Independent analysis puts a TFC semaglutide lot at 97.6%, against 95.9% on the certificate
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.
Change the pH and the co-elution moves
An orthogonal method separates on a different physical principle, so that species co-eluting in the first are likely to resolve in the second. Two runs of the same method at…
Six words a verification badge would need to mean anything
The Journal does not treat a badge as evidence and states so wherever it reports one.
Independent analysis puts a WXT exenatide lot at 96.5%, against 92.6% on the certificate
A reminder that a purity figure is the output of a method, and that methods differ.